1. Field of the Invention
This invention relates to an apparatus for electrically testing multi-core cables and more particularly it relates to a discontinuity test and a defective contact test of the cores of a multi-core cable, such as a communication cable, having a number of cores, each comprising a conductor wire and an insulating cover. Such testing involves automatically separating the cores one by one.
2. Description of the Prior Art
Usually, a communication cable is constructed by using as a structural unit a pair of said cores twisted together or a quad in which four cores are twisted together. Some local communication cables containing a number of cable circuits comprise as many as 2,400 to 3,200 pairs, i.e., 4000 to 6400 cores may be contained in a single cable. In the production of such communication cables, all of these cores have to be tested individually, one by one, to see if there is a defective contact due to an insulation breakdown or a discontinuity. Such testing takes place in an intermediate or final stage of cable production in order to guarantee the quality of each cable. In order to carry out such tests, the inventors of this invention have already proposed an apparatus for testing defective contacts in the cores of a multi-core cable as disclosed in U.S. Pat. No. 4,160,947 and an apparatus for discontinuity testing the cores of a multi-core cable as disclosed in U.S. Pat. No. 4,158,167.
The electrical testing devices for a multi-core cable as described in said two U.S. Patents have greatly reduced the enormous amount of time and labor that was required to connect each core one by one to a measuring terminal with a multi-pole connector. An automatic and efficient defective contact testing and discontinuity testing were realized by the use of each apparatus for these tests. However, there is room for improvement in each of the devices described in said U.S. Patents.
In using the above mentioned apparatus for a discontinuity test of a multi-core cable, the test is carried out by collectively holding the cores at one end in mutually isolated relation, while collectively rendering them conductive at the other end, and picking up a single core one by one from the group of cores at one end. On the other hand, in using the above proposed apparatus for a defective contact test, the test is carried out by collectively rendering the core at one end conductive while holding them in mutually isolated relation at the other end and picking up a single core one by one from the group of cores at one end. As a result, the way to connect the conductor of the group of cores at both ends of a cable in the discontinuity test is converse to that in the defective contact test. In addition, each electrical test is carried out by different methods, in which different steps must be taken separately by each tester for the defective contact test and for the discontinuity test even using the above mentioned efficient apparatuses.